During the TOS era, Starfleet adopted a policy of using painted, standardized parts (saucer sections, engineering sections, and nacelles) for its starships and the original Constitution-class was a product of that time.

Robert April was the first captain of the USS Enterprise (NCC-1701); Lieutenant Commander Christopher Pike was his first officer.

Fashion in the mid 23rd-Century underwent a retro period inspired by the 1960s.

Phase weaponry never entered widespread usage in the late 22nd-Century and Starfleet relied on a new form of "laser" weaponry until the 2260s.

The USS Constellation (NCC-1017) originally came from a different starship class but was ultimately upgraded to a Constitution-class.

Kirk commanded a second five-year mission after TMP.

Following the completion of Kirk's second 5-year mission, he was forced to return to the admiralty as the Commandant of Starfleet Academy; Spock was subsequently promoted to Captain of the Enterprise.

At some point prior to TWOK, the Enterprise was assigned to Starfleet Academy as a cadet training vessel still under Spock's command.

Relations between the Federation and the Klingons took a sharp turn for the worse after Star Trek V and soured the views of many Starfleet veterans (including Kirk and Scotty) towards Klingons.

The Enterprise-B was in the final months of her construction at the time of Star Trek VI.

John Harriman was only the first captain of the Enterprise-B, there were several others that came after him.

The Enterprise-B was decommissioned after 50 years as the longest-serving Federation starship to bear the Enterprise name.

Riker and LaForge had attended a class together as cadets at Starfleet Academy, but didn't really get to know each other during their time there.

The first seven years of the Enterprise-D's service was spent performing a wide variety of missions. The ship was about to finally embark on a long-term (10+ year) deep-space exploration mission at the time of Generations.

Most of these gel pretty well with what I've always imagined (except for a second 5-year-mission. I've never seen the need for it.)

Also, in my continuity, women are wearing miniskirts again.

I think the second 5 year mission comes from the fact that TMP was originally planned to be a new TV series.